Process for drying web material



United States Patent Oifice 3,416,236 Patented Dec. 17, 1968 3,416,236 PROCESS FOR DRYING WEB MATERIAL Geoffrey D. Hnghson, Glens Falls, N.Y., assignor to International Paper Company, New York, N.Y., a corporation of New York No Drawing. Filed Nov. 28, 1966, Ser. No. 597,223 2 Claims. (Cl. 34-23) ABSTRACT OF THE DISCLOSURE A process of drying a web of paper or the like more uniformly and with a reduction in the incidence of overdrying on at least one of its sides by adj'ustably partitioning a rotatable dryer roll interiorly to form a closed zone at the corresponding end of the roll, flowing hi-gh pressure steam into the roll adjacent the closed zone, and flowing low pressure steam or some other medium having a predetermined temperature lower than that of the high pressure steam into the closed zone.

This invention relates to dryer rolls used in the manufacture of pulp and paper. More particularly, it relates to an improvement in the method of and equipment for drying pulp, paper, and other web materials during their manufacture.

Paper and other web materials are dried after their formation on, for instance, a Fourdrinier paper machine by passing them over a series of internally steam-heated dryer cylinders which rotate about their longitudinal axes at high speeds. See, for example, Witham, G. 8.; Modern Pulp and Paper Making; Reinhold Publishing Corporation; New York, 1942; pp. 437 to 453 and Stephenson, J. N. (ed.) Pulp and Paper Manufacture (vol. 3); McGraw- Hill Book Company, Inc.; New York, 1953; pp. 301 to 369.

As a consequence of various ventilation and heat transfer problems arising out of the use of dryer cylinders or rolls, the web material sought to be dried is frequently, not to say commonly, over-dried along one or both of its side edges, while the center portion of the web is being properly dried. This overdrying, in turn, results in difficulties in calendering and winding the web material and can have a deleterious effect on the end use properties thereof.

In an article entitled Improvement of Reel Moisture Profile by Dryer insulation and published March 1959 in Pulp and Paper Magazine of Canada, I. E. Campbell and G. D. Hughson covered experimentation with internal dryer cylinder insulation which involved disposing insulating means (bricks) in annular rings interiorly of a dryer roll near or at its ends. It was reasoned that, if the higher evaporation rate at the sides of the web being dried were due mainly to greater heat flow from the dryer steam to these locations as a result of the dryer head, i.e., end, being unprotected by a condensate film or as a result of the dryer shell interior being scoured by steam, so as to produce an abnormally high overall heat transfer coefficient, then the use of a low-conductivity barrier (the bricks) between the steam and the dryer inner surface should aid in reducing this evaporation rate. The article reported surprisingly consistent and very significant changes in moisture profile as the result of the introduction of the insulation.

It is undoubtedly true that the reason for the lack of industry interest in the Campbell and Hughson article was the obvious impracticality of using insulating material (i.e., bricks) of the type which could, and after not particularly extensive use, did come loose and endangered the roll condensate siphons and systems.

Now, a way has been found to overcome over-drying at the ends of dryer rolls and, at the same time, to overcome the lack of adjustability or adaptability that comes with lining the insides of dryer rolls at their ends with bricks or the like. This was and is the principal object of the present invention.

In process terms, the invention comprises adjustably disposing partitioning means interiorly of a rotatable dryer roll along its longitudinal axis near at least one of the roll ends to form a closed zone defined by the roll end, the partitioning means, and a length of the dryer shell; occupying the closed zone with low pressure steam, condensate, air or water; and, flowing high pressure steam into the remainder of the roll. In apparatus terms, the invention comprises a rotatable dryer roll having partitioning means disposed interiorly thereof along the longitudinal axis of the roll or cylinder, so as to form a closed zone defined by the roll end, the partitioning means, and a length of the dryer shell; means for oocuping the closed zone with low pressure steam, condensate, air or water; and, means to flow high pressure steam intothe remainder of the roll. It is contemplated that air or some other insulating medium can either be flowed into and out of the roll end zones or be sealed into such zones at the installation of the partitioning means.

Clearly, if one partitioning means can be installed in a dryer roll near one of its ends, one or more additional such means can be introduced into the roll so as to achieve adjacent zones near the roll ends in each of which predetermined temperature levels can be achieved by the use of low pressure steam, condensate, air, Water, or some other heating or cooling medium. Accordingly, the installation of more than one partitioning means near a roll end is within the scope of this invention.

What is claimed is:

1. In a process of drying a web material with a rotatable dryer roll having ends and a shell and reducing o-verdrying along at least one side edge of the web material, the steps of adjustably disposing partitioning means interiorly of the roll along its longitudinal axis near at least one of its ends to form a substantially closed zone defined by the roll end, the partitioning means, and the shell; introducing low pressure steam, condensate, air, or water having a predetermined elevated temperature into the closed zone; and, flowing high pressure steam having a higher elevated temperature into the remainder of the roll.

2. The process of claim 1 wherein the web material is paper.

References Cited UNITED STATES PATENTS 2,792,643 5/1957 Guy 34124 2,793,006 5/ 1957 Baby 89 2,870,546 1/1959 Nelson et al 165-89 XR 3,246,401 4/1966 Walser et a1. 34-134 X=R KENNETH W. SPRAGUE, Primary Examiner. 

